Geoscience at the nanometre scale: review of analytical transmission electron microscopy applications

This paper describes applications of analytical Transmission Electron Microscopy (TEM) in the geosciences. The topics include: 1) sulphide-mineral oxidation; 2) trace-metal attenuation by secondary Mn oxides; 3) silicate weathering; 4) transition-metal valence in minerals; and 5) secondary Hg minerals in stream sediments. The main advantage of the analytical TEM is the ability to obtain images, chemical information, and electron diffraction patterns at the nanometre scale. With such high spatial resolution, it is possible to observe physical and chemical features in samples that cannot be resolved with most other techniques. This information can lead to significant improvement in our understanding of the system under investigation. Sample preparation techniques that are used in each study are also described in this paper. The preparation of samples for TEM analysis can be challenging because of the heterogeneity commonly encountered in geological materials, the fragility of some geological samples (e.g., low-temperature minerals), and the need to maintain spatial relationships present in the samples. The sample preparation techniques presented are specific to the needs of the study and the appropriateness of these methods is demonstrated by the high quality analytical TEM data that are obtained. RÉSUMÉ Cet exposé décrit des applications de la microscopie électronique à transmission analytique dans les sciences de la terre. Les aspects étudiés comprennent : 1) l'oxydation des minéraux sulfurés; 2) l'atténuation des métaux-traces par des oxydes de Mn secondaires; 3) la silicatisation météorique; 4) la valence des métaux de transition dans les minéraux; et 5) les minéraux de Hg secondaires dans les sédiments fluviatiles. Le principal avantage qu'offre la MET analytique est la possibilité d'obtenir des images, des données chimiques et des figures de diffraction des électrons à l'échelle nanométrique. Une résolution spatiale aussi élevée permet l'observation dans les échantillons de propriétés physiques et chimiques impossibles à éclaircir au moyen de la majorité des autres techniques. De tels renseignements peuvent mener à une amélioration marquée de notre compréhension du système à l'étude. Cet exposé décrit en plus les techniques de préparation des échantillons utilisées lors de chaque étude. La préparation des échantillons à une analyse MET peut s'avérer compliquée en raison de l'hétérogénéité que présentent communément les matières géologiques, de la fragilité de certains échantillons géologiques (p. ex. minéraux à basse température) et de la nécessité de maintenir les liens spatiaux présents dans les échantillons. Les techniques de préparation des échantillons présentées sont propres aux besoins de l'étude; les données de haute qualité obtenues des analyses MET témoignent de la pertinence de ces méthodes. [Traduit par la rédaction

Sea buckthorn berries <i>Hippophae rhamnoides</i> L. predict size and composition of a great tit population <i>Parus major</i> L.

In seasonal environments variation in food abundance in the non-breeding season is thought to affect songbird population dynamics. In a unique tit-sea buckthorn berry system we can estimate the berry abundance and both the tit consumption and population dynamics. Six hundred nest boxes were available to great and blue tits Cyanistes caeruleus for breeding in spring and roosting in winter. We followed the dynamics including the recapture histories of individually marked great tits from 2008 to 2014. In each year we estimated 1) the winter sea buckthorn berry availability, 2) an index of berry consumption in December based on the colour of the faeces of roosting birds, 3) the number of breeding great and blue tits, 4) both recapture probability and the return rate of the great tits and 5) immigration rates. December berry abundance positively predicted the number of breeding pairs of both species in the subsequent season and great tit return rates in the second half of the winter. There was support for a sex specific berry effect on the adult return rate in the great tit: female return rate was associated less strongly to berry abundance than male return rate. This skewed the sex ratio of the local breeders in the following breeding season. Intriguingly, annual berry consumption in December was not related to berry abundance, and individuals consuming more berries tended to have slightly lower return rates. Reproductive rate was not related to berry abundance. There was hardly support for a relation between immigration rates of first year breeders and berry abundance. Taken together these results imply that berry stock not only affected population size but also the population composition through sex specific exchange with the surroundings. Since population density covaried with berry abundance, density dependent effects provide an alternative explanation for the patterns observed